Hello techs,
This is my first post, I hope I wish I came here sooner...

I own a Sears Craftsman DGT6000 with a Kohler 27HP (175hrs, 7 yrs old). It started making a huge backfire thru the carb. I checked compression, cylinder 1 = 150, cylinder 2 = 0. I pulled the head on cylinder 2 and discovered the hydraulic lifters were frozen wide open. I removed them and cleaned them internally, black tar came out of both, I suspect the holes got plugged and the oil was stuck inside. I put the lifters back in and now I had 150 compression on both! I noticed the exhaust lifter was not moving much, the engine sounded perfect at idle, then I when took it over 1800 rpm it would begin back firing thru the carb. I pulled the engine out and cracked the case open, the cam was worn down to a small bump for this exaust lifter. I replaced the cam (matching the dots on the cam & crank). Now it wont even try to start! I have replaced all four push rods, a couple were slightly bent, not seen by the naked eye, they wobled when I rolled them on a flat surface. I also replaced both valves on cylinder 2, just in case the stems were slightly bent. Still no cigar!, All it does is turn over and it will have a light back fire (puff/spit) out the carb when I close then open the choke.
I have pulled the engine out two more times, once to spin the cam 180 degrees (even though the service manual makes no mention of TDC). Another to confirm the cam lobes match up to the old one and to have a certified mechanic confirm the timing looks right. This has me baffled, it ran, though be it crappy, it ran w/a bad cam, lifters, push rods, and valves. Now, it is all replaced and doesnt even try. Please help, before I take a baseball bat to this thing!

Also, I have checked the spark plug gap 3 times and I have fire.
I have sprayed fuel in the cylinder and put the spark plug in and doesnt seem to do a thing. When I spun the cam 180 degrees, it sounded identical.

I'm not real familiar wiht that motor, and it's realy hard being right when you are going on what I know, from what youve posted. Not even seeing the engine....
But here goes:
The carb needs work.....
Try some starter fluid instead of gas and see if it will run.
Take some pictures of the carb and post them.
I think your are going to have to get the carb apart and clean with B12 chemtool.
You may have gotten some of the throttle linkage reversed when you worked on the heads, check that again, look for broken govenor springs..... or an open choke?

Thanks for your response.
I was thinking an issue w/the carb.
I put a work shop paper towel between the intake and head, turn the engine over and it is bone dry.
I am attaching pics, I was able to keep most the linkage together when pulling the engine. The choke butterfly opens and closes, when I open the choke is when the carb spits/backfires lightly. The throttle appears to be working.

It has a vacuum operated fuel pump. The vacuum line is NOT blocked by oil, I blew it out. When I disconnect from the carb and turn the engine over it pumps fuel. When I turn the key on the wire going to the bottom of bowl on carb gets 12v. Fuel filter is brand new and facing the correct direction. I even took the carb to a local shop and had them do a test on the diaphram thing mounted on the bottom of the bowl. All checks out. I will say though, when I turn the engine over and over, then pull the plugs, they do not seem wet like I think I should see. I have sprayed fuel and ether into the cylinder and doesnt seem to help. Same old spit out the carb every tenth turn or so.

Have you had the float bowl off ? If not, the best way I know is to take the bowl off and let the float down - the needle valve should come out of the main jet (I am NOT familiar with this carb. so probably someone else knows more about it). It just sounds to me like you are not getting fuel thru the carb. into the cylinders. If you are sure the intake and exhaust vlaves are opening and closing and you get spark -- it seems like it has to be fuel.

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